Intramedullary Fixator. Using the Angular Stable Locking System (ASLS). Angular stable

Intramedullary Fixator. Using the
Angular Stable Locking System (ASLS).
Angular stable
locking concept
for intramedullary
nails
Intramedullary Fixator. Using the
Angular Stable Locking System (ASLS).
What is ASLS?
How does ASLS work?
The Angular Stable Locking System
(ASLS) provides the ability to create a
fixed-angle construct to an intramedullary nail. Therefore, it combines the
advantages of angular stability and
a minimally invasive approach. ASLS
together with an intramedullary nail
form the principle of the Intramedullary
Fixator.
The system consists of a screw with three outer
diameters and a resorbable sleeve.
The resorbable sleeve is placed on the screw tip which
has the smallest screw diameter and is pushed into
the locking hole of the nail.
During screw advancement, the resorbable sleeve is
expanded by the larger middle diameter. Radial
expansion of the sleeve and its fixation in the nail
creates the angular stability.
ASLS – a milestone in nail
development
ASLS reduces the number of influencing variables in fracture treatment and
improves conventional nailing by
offering controlled stability throughout
the procedure. ASLS represents a milestone in nail development: a truly
locked construct offering angular stability to intramedullary nails.
History of Nailing (Synthes/AO)
1940
Introduction of IM
nailing technique by
Gerhard Küntscher
1959/1960
AO (Standard) Nails
1969
First “locked” nail
“Detensor”by
Gerhard Küntscher
1987/1988
First “locked” nails
by Synthes: AO
Universal Femoral
and Tibial Nails
1997
First cannulated
nails: Cannulated
Femoral Nail, Proximal Femoral Nail,
Distal Femoral Nail
Where can I use ASLS?
ASLS is particularly indicated in cases where increased stability is needed, for
example in fractures closer to the metaphyseal area or in poor quality bone.
ASLS can be used in combination with all Synthes cannulated titanium nails as
an alternative to standard locking screws. It is especially suited for the use with
the Expert Nailing System.
1
Pre-OP x-ray, 15 days
after primary treatment
with Ex-Fix
Post-OP x-ray, 3 days
after treatment with
Expert Tibial Nail and
ASLS
Clinical problem:
lack of stability in a
complex distal tibia
fracture1
Solution of the clinical
problem:
stable fixation of the
complex fracture1
X-rays: Prof. Höntzsch, BG Unfallklinik Tübingen, 2008/09
2004
Introduction of the Expert
Nailing System: Expert
Tibial Nail, Proximal
Femoral Nail Antirotation
2006
Expert Humeral Nail,
Expert Retrograde/
Antegrade Femoral Nail
2007
Expert Lateral Femoral
Nail, Expert Hindfoot
Arthrodesis Nail
2009
Introduction of the Angular
Stable Locking System (ASLS)
Intramedullary nails become
truly locked implants
Benefits of the Intramedullary Fixator
according to AO Principles
Stability
Increased stability: a stiff construct
reduces the risk of secondary loss of
reduction.2
More stable
2.5
2
Stiffness (kN/mm)
1.5
Mean value
Increase in stability
1
0.5
Mean value
0
Screw
type
Conventional screws
Angular stable screws
Increased stiffness with angular stable screws
compared to conventional screws
Less fracture site movement:
mechanical properties of resorbable sleeve
are maintained during initial 12 weeks
of healing providing 80% less fracture site
motion.3
Fewer screws provide equal
stability: higher resistance to construct
failure with angular stable locking
proximally and distally.4
2
Publication: Angle stable interlocking screws improve
construct stability of intramedullary nailing of distal tibia
fractures: a biomechanical study, Horn J, Linke B,
Höntzsch D, Gueorguiev B, Schwieger K, Injury (accepted)
3
Internal testings: RMS Report A08_06090_2, Performance
Test for ASLS Resorbable, August 2008
4
Speech: Schwieger K, Gueorguiev B, Lawson-Smith M,
Windolf M, Stoffel K. Biomechanisches Potential winkelstabiler Marknagelverriegelung bei distalen Tibiafrakturen,
DGU, 2008
14,000
Cycles to osteotomy gap widening >5º
Note: certain fracture patterns may require more than two ASLS screws or
ASLS screws in more than one plane to
achieve optimal stability.
Two screws
with the
strength of
three
16,000
12,000
10,000
8000
6000
Mean value
Mean value
Same cycles
with fewer screws
4000
2000
0
Screw
type
Conventionally locked construct with
three conventional screws
Two ASLS screws in one plane are as stable as
three conventional screws in two planes
Angular stable construct with two
angular stable screws
Better hold: trend to superior stability of
angular stable construct, especially in poor
quality bone and in fractures closer to the
metaphyseal area.5
Better hold
1.4
Poor quality bone
1.2
1
Decreased fracture
site motion
Gap angle at 500N (º)
0.8
0.6
0.4
0.2
0
0
0.01
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
Conventional
BMD (g/cm3)
Angular Stable
Fracture gap angle at 500N is significantly smaller for angular
stable construct in 6 out of 8 bone pairs. This effect is most
prominent in low BMD (Bone Mass Density)
Controllable stability: degree of stability can
be determined by surgeon (free choice between
angular stable and conventional screws).6
Relative stability: principle of relative stability
and secondary bone healing remain valid.7
Secondary
bone healing
with callus
5
Publication: Angle stable interlocking screws improve construct stability of
intramedullary nailing of distal tibia fractures: a biomechanical study,
Horn J, Linke B, Höntzsch D, Gueorguiev B, Schwieger K, Injury (accepted)
6
Speech: Schwieger K, Gueorguiev B, Lawson-Smith M, Windolf M,
Stoffel K. Biomechanisches Potential winkelstabiler Marknagelverriegelung
bei distalen Tibiafrakturen, DGU, 2008, Wilhelm-Roux-Preis 2008
gewonnen
7
X-rays: Prof. Höntzsch, BG Unfallklinik Tübingen, 2008/09
5 days post-OP
6 months post-OP
The existence of callus shows that the principle of secondary bone healing with
callus is also valid when using the angular stable locking system.
0.5
Benefits of the Intramedullary Fixator
according to AO Principles
Anatomic reduction
Reduced risk of secondary loss of reduction8
Conventional screws
Significant medial and lateral tilting of conventional construct during testing
Angular stable screws
(experimental design)
Stable
reduction
8
Poster: Schwieger K, Tröster S, Gueorguiev B, Höntzsch D, Linke B: Ist das Prinzip der
winkelstabilen Marknagelstabilisierung eine viel versprechende Option bei der Versorgung
distaler Tibiafrakturen? Biomechanica V, Hamburg, 2005.
No lateral or medial tilting of angular stable construct during testing
Preservation of blood supply
Minimally invasive approach:
ASLS combines the advantages of a minimally invasive
intramedullary nailing approach with the advantages of
angular stability.
Minimally
invasive
Minimally invasive insertion of an Expert Tibial Nail
Early, active mobilization
Early
mobilization
100
% of patients with full weight bearing
Rehabilitation:
stable fixation, provided by ASLS, permits controlled,
early, active rehabilitation that promotes optimal
recovery.9
75
50
25
0
0
1
2
3
4
5
6
7
8
9
10
11
12
13
Number of weeks after surgery
9
First clinical results ASLS, 2008/2009
First clinical results ASLS, 2008/2009
11
Braten, M., Helland, P., Grontvedt, T., Aamodt, A., Benum, P., and Molster, A. External
Fixation Versus Locked Intramedullary Nailing in Tibial Shaft Fractures: a Prospective,
Randomised Study of 78 Patients. Arch.Orthop.Trauma Surg. 2005;125(1):21-6.
10
First clinical results show that the average time to full weight-bearing of
23 tibia fracture patients is significantly shorter when treated with ASLS
(9.4 weeks)10 in contrast to conventional screws (12 weeks)11
14
SE_238775 AA
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Intramedullary Fixator. Using the
Angular Stable Locking System (ASLS).